Where do dogs go when owners go to prison?

Where do dogs go when owners go to prison?

My brother was arrested last October and I've had his 13 yr old pit since. We can't keep him much longer due to deed restrictions, we can only have 2 dogs (which are our 2 labs). If anyone has ANY ideas or suggestions who I can contact to help place him in a loving home, I'd deeply appreciate any help. He is highly UNadoptable due to his age and skin allergies, I'm 99.9% sure if I took him to the humane society, he'd be put down. He's an awesome animal and I'd hate to see him put down, he acts like a puppy--he's got so much energy! Help!